This invention relates to a vacuum modulating air control valve which significantly reduces exhaust emissions by intermittently introducing air into the intake manifold of internal combustion engines under certain operating conditions. More particularly, the invention relates to a modulating air control valve having a unidirectional flow valve, or check valve, which prevents deterioration of the internal components of the valve, thereby significantly increasing the operational life span of the valve.
Due to recent air quality control regulations passed by both federal and state legislatures, the automotive industry has developed various emission control devices to reduce the exhaust pollutants of internal combustion engines. These devices have been numerous in nature and have typically included closed crankcase ventilation systems, spark advance servo mechanisms and catalytic converters. However, recently it has been discovered that exhaust emissions can be substantially reduced by use of a modulating air control valve which introduces ambient air directly into the intake manifold of an internal combustion engine in an amount determined by the vacuum differential between the intake manifold and a vacuum signal source, such as the ported vacuum at a carburetor. The ambient air introduced into the intake manifold in such manner, provides a more complete burning of the fuel at a lower combustion temperature thereby decreasing the formation of pollutants.
Typically, the prior art modulating air control valves utilize a resilient diaphragm which cooperates with a valve seat. This diaphragm opens and closes air bleed orifices within the valve in response to pressure differentials between the ported vacuum source and the intake manifold of the engine. When the diaphragm is modulated away from the valve seat, a plurality of small flow orifices are opened to allow ambient air to pass through the valve and into the intake manifold. Alternatively, when the diaphragm is biased against the valve seat, air flow through these orifices is discontinued. Although these control valves reduce pollutants during initial operation, their effectiveness rapidly diminishes during prolonged use.
One of the major deficiencies of the prior art modulating air control valves is the rapid degradation of the resilient diaphragm. Due to the diaphragm being in direct flow communication with the intake manifold, hydrocarbon fumes produced in the intake manifold during engine operation which are not entirely scavanged through the exhaust system tend to migrate toward and contact the diaphragm during engine-off conditions. These hydrocarbon fumes react with the elastomeric diaphragm material, causing the diaphragm to swell and lose its resiliency and eventually even split or crack. This swelling and loss of resiliency either causes the valve to leak during engine operation or inhibits the opening of the valve.
A further deficiency of the prior art valves is their failure to protest against "backfires" which occasionally occur during engine operation. A "backfire" results from the premature detonation of the air/fuel mixture within the intake manifold of an engine. This premature detonation or explosion causes a high pressure pulse to be transmitted toward the valve. The pulse in many instances causes carbon or dirt particles contained in the intake manifold to lodge into the diaphragm and valve and, in extreme instances, even causes the valve body to crack or shatter.
Additionally, the plurality of small air orifices of the prior art valve tend to become clogged with dirt particles even during normal usage, thereby severely restricting the amount of ambient air introduced into the intake manifold.
In most instances, such deterioration of the diaphragm or clogging of the flow orifices requires a complete replacement of the valve.